Increasing numbers of sports, age, and trauma related injuries like broken bones, worn out joints, and torn ligaments have heightened the demand for bio-materials capable of treating orthopedic injuries. In response, companies have developed bone cements to attach various objects to bone, and bone fillers capable of treating bone fractures and other bone defects. There is also a need for a bio-material capable of stimulating bone formation and growth and a material for providing spinal fusion. Most existing bio-materials are made of calcium phosphates that promote significant new bone formation or relatively inert hardening polymers like polymethylmethcrylate (“PMMA”) that are poorly biocompatible and do not promote new bone formation or spinal fusion without the use of additional fixation devices.
A number of calcium phosphate based compositions have been developed as biomaterials in recent years. For example U.S. Pat. No. 6,331,312 issued to Lee et al., discloses an injectable calcium phosphate based composite useful as a bone filler and cement. The disclosed material is bio-resorbable and is designed for use in the repair and growth promotion of bone tissue as well as the attachment of screws, plates and other fixation devices. Lee's composition does not expand while setting and does not promote significant new bone formation, nor provide spinal fusion. Many existing calcium phosphate based fillers and cements have high molar ratios of Ca to P making them poorly reabsorbable. Furthermore, a recent FDA release warns of serious complications from the use of existing calcium phosphate based bone fillers in treating fractures of the spine (FDA Public Health Web Notification, “Complications Related to the Use of Cement and Bone Void Fillers in Treating Compression Fractures of the Spine,” originally published Oct. 31, 2002, updated, May 27, 2004.)
Generally, current calcium phosphate cements lack the characteristic of a successful compound for providing spinal fusion. In fact, recent studies have investigated the ability of bone void fillers to provide spinal fusion, however, the results have demonstrated that current bone void fillers do not provide adequate spinal fusion to be successful replacement for current bone fusion inducing biomaterial like IMPDH and BMP-2.